'Un banc, un arbre, un benchmark .....'
This one is located on a stone pillar that marks the old electoral ward of Usher's Quay at the south-east corner of Sarah Bridge on the South Circular Road in Dublin. Perhaps it is not a true benchmark.
Below: The 'mark on the ward marker stone pillar.
Above: The 'mark is located atop the stone pillar to the left of the bench.